the idea came from this Applied Science Video:
Electroluminescent paint and multi-channel control circuit
21 Nov 2018 starting at 11:25
there is a link to amazon for a element – and it is not available to delivery to germany 🙁
so i went on with some help of friends and found
| dimensions | voltage | power | current | resistance (guess) | power@ 6V | power@ 9V | power@ 12V | power@ 24V | link |
|---|---|---|---|---|---|---|---|---|---|
| 70mm x 15mm | 12V | 70W | 5,8A | 2,06R | 17W | 39W | 70W | 280W | HALJIA 12V 70W Wired MCH Metal Ceramic Heating Plate Heating Element 70mm x 15mm |
| 70mm x 15mm | 24V | 110W | 4,6A | 5,2R | 7W | 15,6W | 27W | 110W | Haljia 24V 110W Wired MCH Metal Ceramic Heating Plate Heating Element 70mm x 15mm |
| 40mm x 40mm | 12V | 48W | 4A | 3R | 12W | 27W | 24W | 192W | Haljia 12 V48 W Wire MCH Metal Ceramic Heating Plate Heating Element 40 mm x 40 mm |
| 40mm x 40mm | 24V | 96W | 4 | 6R | 24W | 13,5W | 48W | 96W | Haljia 24 V96 W WIRED MCH Metal Ceramic Heating Plate Heating Element 40 mm x 40 mm |
to get an idea of how much power i actually need i had a look at the small commercial IR-Heaters and Hot-Plates –
they all have about 800W:
180mm * 235mm = 42300 mm² = 423 cm²
a = 60mm * 60mm = 3600 mm² = 48 cm (1x4)
b = 60mm * 80mm = 4800 mm² = 48 cm (2x2)
c = 60mm * 90mm = 5400 mm² = 54 cm² (1x6)
d = 60mm * 120mm = 7200 mm² = 72 cm² (1x8)
e = 120mm * 60mm = 7200 mm² = 72 cm² (2x4)
f = 120mm * 90mm = 10800 mm² = 108 cm² (2x6)
g = 120mm * 120mm = 14400 mm² = 144 cm² (2x8)
423 cm² == 800W
1 cm² == x
x = 800W * 1cm² / 423cm² = 1,89W
a = 800W * 36cm² / 423cm² = ~68W (1x4)
b = 800W * 48cm² / 423cm² = ~91W (2x2)
c = 800W * 54cm² / 423cm² = ~102W (1x6)
d = 800W * 72cm² / 423cm² = ~136W (1x8)
e = 800W * 72cm² / 423cm² = ~136W (2x4)
f = 800W * 108cm² / 423cm² = ~204W (2x6)
g = 800W * 144cm² / 423cm² = ~272W (2x8)
30x40mm: ~23W/module
60x15mm: ~17W/modulethen i calculated the resistance of the found element to check on what wattage i can do at what voltages:
U = R*I
P = U*I
→ P = U*(U/R)(i added these *guesses* in the table above)
So I decided to go with the 70x15mm 24V model.
and will update here if i found how this works out..
and for the first test setup i will go with the concept
12V→ 27W / module
so definitive more then enough..
as power supply i will use a MeanWell GST280A48-C6P
(reichelt) with an fitting connector (reichelt)
to get a 5V for the controller i will go with a recom R-78HB50-05 (VIN: 9-72V)
and for switching the power to the heating elements i will use IRLB4030PBF – MOSFET N-LogL 100V 180A 370W 0,0043R TO220AB
and to drive this a BC 550C as mentioned in this nice article:
Schalten und Steuern mit Transistoren III – Mit MOSFETs höhere Ströme schalten
for temperature measurement i use a Adafruit Universal Thermocouple Amplifier MAX31856 Breakout with an Thermocouple Type-K Glass Braid Insulated – K
and have the plan to use a Melexis IR thermometer
i have ordered a MLX90614ESF-BAA-000-TU
i hope that with this i can precisely track the surface temperature..
so when all the parts arrive i can go on.. with building.
for the Controller i plan to write it in CircuitPython and run it on an adafruit (maybe ItsyBitsyM4) PyBadge –
for now i just want to use the arduino serial plotter or similar with an second CDC-device enabled to log the progress and the flash-drive function of CircuitPython for a text-file with the temperature-profile.
i have written a request in the adafruit CircuitPython forum if there are any PID controller things out there…